			var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 3         var base64DecodeChars = new Array(
 4             -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 5             -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 6             -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
 7             52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
 8             -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
 9             15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
10             -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
11             41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1);
12         
13         //加密方法   
14         function base64encode(str) {
15             var out, i, len;
16             var c1, c2, c3;
17             len = str.length;
18             i = 0;
19             out = "";
20             while(i < len) {
21                 c1 = str.charCodeAt(i++) & 0xff;
22                 if(i == len) {
23                     out += base64EncodeChars.charAt(c1 >> 2);
24                     out += base64EncodeChars.charAt((c1 & 0x3) << 4);
25                     out += "==";
26                     break;
27                 }
28                 c2 = str.charCodeAt(i++);
29                 if(i == len) {
30                     out += base64EncodeChars.charAt(c1 >> 2);
31                     out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
32                     out += base64EncodeChars.charAt((c2 & 0xF) << 2);
33                     out += "=";
34                     break;
35                 }
36                 c3 = str.charCodeAt(i++);
37                 out += base64EncodeChars.charAt(c1 >> 2);
38                 out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4));
39                 out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6));
40                 out += base64EncodeChars.charAt(c3 & 0x3F);
41             }
42             return out;
43         }
44         
45         //解密方法
46         function base64decode(str){
47             var c1, c2, c3, c4;
48             var i, len, out;
49             len = str.length;
50             i = 0;
51             out = "";
52             while (i < len) {
53                 /* c1 */
54                 do {
55                     c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
56                 }
57                 while (i < len && c1 == -1);
58                 if (c1 == -1) 
59                     break;
60                 /* c2 */
61                 do {
62                     c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
63                 }
64                 while (i < len && c2 == -1);
65                 if (c2 == -1) 
66                     break;
67                 out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));
68                 /* c3 */
69                 do {
70                     c3 = str.charCodeAt(i++) & 0xff;
71                     if (c3 == 61) 
72                         return out;
73                     c3 = base64DecodeChars[c3];
74                 }
75                 while (i < len && c3 == -1);
76                 if (c3 == -1) 
77                     break;
78                 out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));
79                 /* c4 */
80                 do {
81                     c4 = str.charCodeAt(i++) & 0xff;
82                     if (c4 == 61) 
83                         return out;
84                     c4 = base64DecodeChars[c4];
85                 }
86                 while (i < len && c4 == -1);
87                 if (c4 == -1) 
88                     break;
89                 out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
90             }
91             return out;
92         }